Render region into header

docs/src/configurations/config-file-format.md

@@ -9,6 +9,9 @@ max_concurrent_requests = 5
 
 default_region = "us-east-1"
 
+[ui.header]
+show_region = true
+
 [ui.bucket_list]
 default_sort = "default"
 
@@ -83,6 +86,13 @@ The default region to use if the region cannot be obtained from the command line
 - type: `string`
 - default: `us-east-1`
 
+### `ui.header.show_region`
+
+Whether to display the AWS region resolved by the client (e.g. from the `--region` flag, `AWS_REGION` env var, or AWS profile) in the top-right of the header bar. The label is hidden automatically when the resolved region is just the configured `default_region` fallback.
+
+- type: `bool`
+- default: `true`
+
 ### `ui.bucket_list.default_sort`
 
 The default sort order of the bucket list.

src/app.rs

@@ -72,11 +72,24 @@ pub struct App {
     notification: Notification,
     is_loading: bool,
     pending_single_bucket_reload: Option<BucketItem>,
+    header_region: Option<String>,
 }
 
 impl App {
     pub fn new(mapper: UserEventMapper, client: Client, ctx: AppContext, tx: Sender) -> App {
         let ctx = Rc::new(ctx);
+        // Use the region the AWS SDK actually resolved (honors --region CLI arg,
+        // AWS_REGION / AWS_DEFAULT_REGION env vars, and AWS profile config).
+        // Suppress the label when the SDK fell back to the configured default,
+        // so users who haven't set anything explicitly don't see a misleading
+        // "[us-east-1]" in the header.
+        let resolved_region = client.region();
+        let header_region =
+            if !ctx.config.ui.header.show_region || resolved_region == ctx.config.default_region {
+                None
+            } else {
+                Some(resolved_region.to_string())
+            };
         App {
             app_objects: AppObjects::default(),
             page_stack: PageStack::new(Rc::clone(&ctx), tx.clone()),
@@ -87,6 +100,7 @@ impl App {
             notification: Notification::None,
             is_loading: true,
             pending_single_bucket_reload: None,
+            header_region,
         }
     }
 
@@ -1023,7 +1037,9 @@ impl App {
 
     fn render_header(&self, f: &mut Frame, area: Rect) {
         if !area.is_empty() {
-            let header = Header::new(self.page_stack.breadcrumb()).theme(self.ctx.theme());
+            let header = Header::new(self.page_stack.breadcrumb())
+                .theme(self.ctx.theme())
+                .region(self.header_region.clone());
             f.render_widget(header, area);
         }
     }

src/config.rs

@@ -39,6 +39,8 @@ pub struct Config {
 #[optional(derives = [Deserialize])]
 #[derive(Debug, Clone, SmartDefault)]
 pub struct UiConfig {
+    #[nested]
+    pub header: UiHeaderConfig,
     #[nested]
     pub bucket_list: UiBucketListConfig,
     #[nested]
@@ -51,6 +53,13 @@ pub struct UiConfig {
     pub theme: Theme,
 }
 
+#[optional(derives = [Deserialize])]
+#[derive(Debug, Clone, SmartDefault)]
+pub struct UiHeaderConfig {
+    #[default = true]
+    pub show_region: bool,
+}
+
 #[optional(derives = [Deserialize])]
 #[derive(Debug, Clone, SmartDefault)]
 pub struct UiBucketListConfig {
@@ -258,6 +267,23 @@ object_dir_bold = false
         assert_eq!(config.ui.theme.dialog_selected, Color::Cyan);
     }
 
+    #[test]
+    fn header_show_region_defaults_to_true_when_omitted() {
+        let config = parse_config("");
+        assert!(config.ui.header.show_region);
+    }
+
+    #[test]
+    fn header_show_region_can_be_disabled() {
+        let config = parse_config(
+            r#"
+[ui.header]
+show_region = false
+"#,
+        );
+        assert!(!config.ui.header.show_region);
+    }
+
     #[test]
     fn invalid_theme_color_is_rejected() {
         let result = toml::from_str::<OptionalConfig>(

src/widget/header.rs

@@ -1,6 +1,6 @@
 use ratatui::{
     buffer::Buffer,
-    layout::{Margin, Rect},
+    layout::{Alignment, Margin, Rect},
     style::{Color, Stylize},
     widgets::{Block, Padding, Paragraph, Widget},
 };
@@ -25,6 +25,7 @@ impl HeaderColor {
 #[derive(Debug, Default)]
 pub struct Header {
     breadcrumb: Vec<String>,
+    region: Option<String>,
     color: HeaderColor,
 }
 
@@ -40,6 +41,11 @@ impl Header {
         self.color = HeaderColor::new(theme);
         self
     }
+
+    pub fn region(mut self, region: Option<String>) -> Self {
+        self.region = region.filter(|s| !s.is_empty());
+        self
+    }
 }
 
 impl Widget for Header {
@@ -51,8 +57,14 @@ impl Widget for Header {
 impl Header {
     const DELIMITER: &'static str = " / ";
     const ELLIPSIS: &'static str = "...";
+    const REGION_GAP: usize = 2;
 
     fn render_header(self, area: Rect, buf: &mut Buffer) {
+        if self.region.is_some() {
+            self.render_header_with_region(area, buf);
+            return;
+        }
+
         let inner_area = area.inner(Margin::new(1, 1));
         let pad = Padding::horizontal(1);
         let max_width = (inner_area.width - pad.left - pad.right) as usize;
@@ -67,6 +79,54 @@ impl Header {
         paragraph.render(area, buf);
     }
 
+    fn render_header_with_region(self, area: Rect, buf: &mut Buffer) {
+        let pad = Padding::horizontal(1);
+        let block_color = self.color.block;
+        let text_color = self.color.text;
+
+        let block = Block::bordered().fg(block_color).padding(pad);
+        let inner_area = block.inner(area);
+        block.render(area, buf);
+
+        if inner_area.width == 0 || inner_area.height == 0 {
+            return;
+        }
+
+        let total_width = inner_area.width as usize;
+
+        // Region is guaranteed to be Some here; format and measure it.
+        let region_text = format!("[{}]", self.region.as_deref().unwrap());
+        let region_width = console::measure_text_width(&region_text);
+
+        // If the region label doesn't fit, fall back to the breadcrumb-only layout.
+        if region_width + Self::REGION_GAP >= total_width {
+            let breadcrumb_str = self.build_current_key_str(total_width).fg(text_color);
+            Paragraph::new(breadcrumb_str).render(inner_area, buf);
+            return;
+        }
+
+        let breadcrumb_width = total_width - region_width - Self::REGION_GAP;
+
+        let breadcrumb_str = self.build_current_key_str(breadcrumb_width).fg(text_color);
+        let breadcrumb_area = Rect {
+            x: inner_area.x,
+            y: inner_area.y,
+            width: breadcrumb_width as u16,
+            height: inner_area.height,
+        };
+        Paragraph::new(breadcrumb_str).render(breadcrumb_area, buf);
+
+        let region_area = Rect {
+            x: inner_area.x + (total_width - region_width) as u16,
+            y: inner_area.y,
+            width: region_width as u16,
+            height: inner_area.height,
+        };
+        Paragraph::new(region_text.fg(text_color))
+            .alignment(Alignment::Right)
+            .render(region_area, buf);
+    }
+
     fn build_current_key_str(self, max_width: usize) -> String {
         if self.breadcrumb.is_empty() {
             return "".to_string();
@@ -106,7 +166,7 @@ mod tests {
             .into_iter()
             .map(|s| s.to_string())
             .collect();
-        let header = Header::new(breadcrumb).theme(&theme);
+        let header = Header::new(breadcrumb).theme(&theme).region(None);
         let mut buf = Buffer::empty(Rect::new(0, 0, 30 + 4, 3));
         header.render(buf.area, &mut buf);
 
@@ -154,4 +214,26 @@ mod tests {
         ]);
         assert_eq!(buf, expected);
     }
+
+    #[test]
+    fn test_render_header_with_region() {
+        let theme = Theme::default();
+        let breadcrumb = ["bucket", "key01"]
+            .into_iter()
+            .map(|s| s.to_string())
+            .collect();
+        let header = Header::new(breadcrumb)
+            .theme(&theme)
+            .region(Some("eu-central-1".to_string()));
+        let mut buf = Buffer::empty(Rect::new(0, 0, 40, 3));
+        header.render(buf.area, &mut buf);
+
+        #[rustfmt::skip]
+        let expected = Buffer::with_lines([
+            "┌──────────────────────────────────────┐",
+            "│ bucket / key01        [eu-central-1] │",
+            "└──────────────────────────────────────┘",
+        ]);
+        assert_eq!(buf, expected);
+    }
 }